Diagnosis of ARDS or ALI was made according to criteria of the American-European Consensus Conference on ARDS

This prospective, observational study was carried out on 29 patients (24 men and 5 women; median age, 50 years; range, 19 to 70 years): 19 patients with ARDS and 10 patients with ALI. Diagnosis of ARDS or ALI was made according to criteria of the American-European Consensus Conference on ARDS (acute onset of respiratory failure, bilateral infiltrates on chest radiography, pulmonary-artery wedge pressure < 18 mm Hg or the absence of clinical evidence of left atrial hypertension; ALI was considered to be present if Pao2/Flo2 ratio was < 300, and ARDS if Pao2/Flo2 ratio was < 200). ALI/ARDS was observed after major surgery, multiple trauma, head injury, thorax trauma, pancreatitis, pneumonia, or severe sepsis. Exclusion criteria for enrollment of patients were hemofiltration, massive transfusion in the immediately preceding 24 h, medical history of chronic lung disease, and immunosuppressive therapy. 

Diagnosis of ARDS

All patients were receiving mechanical ventilation and standard intensive care support. Severity of illness was scored during the first 24 h after onset of ALI/ARDS using the simplified acute physiology score II (SAPS II) and sequential organ failure assessment (SOFA). For calculation of the SAPS II and SOFA score, which were single determinations during the first day after onset of ALI/ARDS, the worst values of physiologic and clinical variables observed over 24 h were taken in account as originally described. 

BAL (routine protocol for microbiologic culture with 100 mL of 0.9% saline solution sequentially instilled and suctioned in 20-mL portions) was performed in a subsegment of the right middle lobe of lung within 12 h and 24 h after onset of ALI/ARDS. Blood for determination of G-CSF, ENA-78, and IL-8 in serum was obtained from the patients at the same time. The protocol for this study was approved by the Ethics Committee of the Leopold-Franzens-University of Innsbruck.

Recovered BALF volume was not different between the ARDS and ALI groups (ARDS group, 43 mL [range, 28 to 57 mL]; ALI group, 41.5 mL [range, 30 to 56 mL]; p = 0.5819). After collecting BALF in tubes, the fluid retrieved was filtered through sterile gauze and centrifuged at 300g at 4°C for 10 min to remove mucus and cells. The supernatants were aliquoted into cups and frozen at — 80°C until analysis. Blood sampling was performed with three 4-mL syringes and then ice cooled. Blood was allowed to clot and then centrifuged at 1,000g for 10 min at 4°C. Multiple aliquots of serum were frozen at — 80°C until analysis.